Speedy location of optic disc in retinal images

The retinal images are routinely captured by using ophthalmoscopes for locating aberrations due to illnesses like diabetes. The image contains the bright yellow colored optic disc (OD) which makes it difficult to isolate the retinal defects like the hard or soft yellow-exudates by image processing software. The arbitrary angles at which doctor captures the images add to the difficulty in estimating the OD position. If only the OD could be located and covered by a dark mask, the yellow exudates could be isolated with ease. A new set of parameters is introduced and a novel expression for brightness is proposed to isolate the optic disc, after RGB normalization. A recursive positioning based on normalized hue and standard deviation is also discussed.